Hydrocarbon derivatives



.lime 16, 1953 A. w. FRANCIS SEPARTION 0F HYDROCARBONS AND HYDROCARBON DERIVATIVES Filed Sept. 13. 1949 S w .SS w

N @uw NNANH 14N Patented June 16, 1953 SEPARATION -OF HYDROCARBON'S AND HYDROCARBON DERIVATIVES Alfred W. Francis, Woodbury, N. J., assignor to Socony-Vacuum Oil Company, Incorporated, a corporation of New York Application September 13, 1949, Serial No. 115,396

claims. (c1. 26o-96.5)

This invention has to do with the separationl of hydrocarbons and hydrocarbon derivatives of diierent molecular configuration from mixtures containing the same.

I. FIELD OF INVENTION Numerous processes have been developed for the separation of hydrocarbons and hydrocarbon derivatives of different molecular configuration by taking advantage of their selective solubility in selected reagents or solvents from which they may later be separated. Exemplary of hydrocarbon separation procedures is the Edeleanu process, wherein parainic materials are separated from aromatics by virtue of the greater solubilityof aromatics in liquid sulfur dioxide. Lubricant oil solvent rening processes, solvent deasphalting', solvent dewaxing and the like are further examples of the separation of hydrocarbons of different molecular configuration. Typical of selective solvent procedures for separating hydrocarbon derivatives is the separation ofparafn wax, monochlorwax and polychlorwaxes, with acetone as the selective solvent.

This invention is concerned with the general field outlined above, but based upon a different and little-known phenomenon, namely, the differing ability of hydrocarbons and hydrocarbon derivatives to enter into and to be removed from certain crystalline complexes. As used herein, the term complex broadly denotes a combination of two or more compounds.

This invention is predicated upon the knowlv901) found a number of aromatic amines contamlng at least one basic amino group capable of forming double compounds. with certain isomeric phenols. It has also been shown that trans-oestradiol can be separated from the" corresponding cis-compound by forming a difcultly n soluble compoundA of urea and trans-oestradiol (Priewe 2,300,134).

edge that urea and thiourea form complex crys- 4o Kremann (Monating a meta-cresol-urea complex, which was described as an addition compound thelatter compound was separated from the para isomer and then-split up by distillation or with water or acid to obtain pure meta-cresol. The addi-- tion compound of meta-cresol and urea was shown thereafter to have utility as a disinfectant (Priewe 1,933,757). Bentley and Catlow (1,980,-

The forces between urea and the compounds of the foregoing complexes are due to specific chemicalv interactionV Ybetween the functional groups.

One heterocyclic compound, 2:6 lutidine, has

been found to form a crystalline compound with urea, thus aifording a means of separating the lutidine from beta- Aand gamma picolines (Riethof 2,295,606).

Comparatively few aliphatic hydrocarbon derivatives have been known to date to form complex compounds with urea. In German patent application B 190,197, IV d/ 12 (Technical Oil Mission, Reel 143; Library of Congress, May 22,A 1946), Bengen described a method'v for the sepwere designated adducts, which term ap-v parently stems from the anglicized addition product. The adducts are separated into their components, urea and straight chain hydrocarbon or aliphatic oxygen-containing compound, by heating'or by the addition of methanol. water or an aqueous solution.

Thiourea `has also been Aknown to 'form complexes, perhaps the' rst of which' is 'a complex with ethyl .oxalate (Nencki', Berichte I'7,' 780 were described by Angla (Compt. rendus 224, 402-4. and 1166 (1947) The organic compounds recited include cyclic hydrocarbons such as cyclohexane, cyclohexene, .polycyclic terpenes; halides, alcohols and ketones of such cyclic'hydrocarbons; and halides of kshort chain parafns. Crystalline molecular complexes of such compounds are dissociated by water and organic sol- Recently, crystalline molecular complexes of thiourea and certain organic compounds vents to their components, thiourea and a compound of the foregoing type.

III. DEFINITIDNS From the foregoing discussion of prior art (II), it will be clear that a variety of terms have been applied to urea and thiourea complexes. The latter have been rather loosely described as double compounds, addition compounds, diiiicultly soluble compounds, Additions-Produkt, adducts, and crystalline molecular complexes. All of these terms are somewhat ambiguous in that they have also been used to describe products or complexes of different character than the urea complexes under consideration. This is particularly so with the term adduct, and the related term "unadducted material. While the term adduct is simple and convenient, it is an unfortunate designation, inasmuch as it confuses these complexes With other substances known in the chemical art. Speciiically, adduct has been applied to Diels-Alder reaction products, formed by reaction of conjugated diolefins and oleilns and their derivatives. As is Well known, Diels-Alder products, as a rule, do not revert to their original constituents when heated or treated with water, acids, solvents, etc. Moreover, the term adduct has been dened earlier as The product of a rcaction between molecules, which occurs in such a way that the original molecules or their residues have their long axes parallelto one another. (Concise Chemical and Technical Dictionary). Further ambiguity is introduced by the term adduction, which has been defined as oxidation. (Hackh).

To avoid the foregoing conflicting terminology, several related terms have been coined to dene with greater specificity the substances involved in the phenomenon under consideration. As contemplated herein and as used throughout the speciiication yand appended claims, the following terms identify the phenomenon:

Plexad-a revertible associated complex comprising a plexor, such as urea, and at least one other compound; said plexad characterized by reverting or decomposing, under the iniiuence of heat and/ or various solvents, to its original constituents, namely, a plexor and at least one plexand.

Plexand-a compound capable of forming a plexad with a plexor, such as urea. and thiourea; compounds of this character differ in their capacity to form plexads, depending upon various factors described hereinafter.

Antiplex--a compound incapable of forming a plexad with a plexor.

Plexor-a compound capable of forming a Dlexad ywith a plexand; such as urea and thiourea.

Plexate-to form a plexad.

Plexation-the act, process or effect of plexating.

IV. 'OU'ILINE OF INVENTION It has now been found that the separation procedures used hitherto can be improved substantially by the use of certain solvents With a plexor.

As indicated above, urea plexads and thiourea plexads have been formed by contacting a mixture containing a plexand and an antiplex, with urea or thiourea carried in water or an alcohol solution, whereupon a urea or thiourea plexad was formed. The plexad was then separated from the antiplex by decantation, iiltration or similar means, and the plexad was decomposed into its components by heating or by contact with a suitable solvent.

Plexation procedures of the foregoing character, however, are subject to one or more shortcomings. For example, the solubility of urea and/ or thiourea in various solvents is not as hish as desired, thus reducing the opportunity for complete reaction or plexation. The solubility of urea in methanol, by way of illustration, is onlyn of the order of 23 per cent by weight at 25 C., and with water is about 5e per cent. In addition, relatively7 Slow reaction rates characterize certain of the urea-solvent and/or thiourea-solvent systems previously used, possibly because of the extremely low solubility of hydrocarbons in Water. While methanol solutions react faster than water solutions, urea is depleted much faster because of the lower concentrations of urea in methanol, and since plexation is reversible, the extent of reaction is limited" unless excessive amounts of urea solution are used.

The shortcomings of previous plexation procedures havenow been overcome by using certain aqueous acetic acid solutions as the urea or thiourea solvents.

In some manner, as yet not thoroughly understood, certain aqueous acetic acid solutions cooperate with the plexor to provide a more effective plexation. By way of speculation, and in no sense a limitation upon the subject matter described and claimed herein, it is possible that the following factors are involved. As an organic liquid, acetic acid dissolves some hydrocarbon, for example, and thus greatly increases its solubility and, therefore, its reactivity in an aqueous solution. But, unlike neutral solvents such as methanol, acetic acid does not greatly decrease the solubility of urea in aqueous solutions, since it forms the highly soluble and reactive urea diacetate. Anhydrous acetic acid dissolves only about l1 per cent of urea at 25 C., but an 87.5 per cent acetic acid solution in urea dissolves over 40 per cent of urea at 25 C. Solutions recommended herein vary from about 20 per cent to about 88 per cent acetic acid at 25 C., with a 50 per cent solution providing excellent results. The latter solution dissolves about 5i) percent of urea, that is, the solution contains 50 per cent of urea, 25 per cent of acetic acid and 25 per cent of water.

Organic acids in addition to acetic acid can be used advantageously herein, including: citric,-

tartaric, formic, propionic and oxalic. Mineral acids, such as hydrochloric, sulfuric and nitric, augment the solubility of urea in aqueous solutions, but they have not been found efficacious herein because the resulting high hydrogen ion concentration appears to inhibit the plexation in part if it is more than one-tenth normal in concentration, and to inhibit the plexation completely if it is more than one normal in concentration. A hydrogen ion concentration of at least about 10-3 appears to be necessary to augment the solubility of urea, but should not be greater than about 10-1 to avoid an inhibiting effect upon the plexation.

V. OBJECTS It is an object of this invention, therefore, to provide an effective means for separating hydrocarbons and hydrocarbon derivatives of different molecular conguration from mixtures containing the same.

It is also an object of this invention to separate a plexand from an antiplex, and to provide a plexand substantially free of an antiplex,

Another important object is the provision of a continuous method of separation of said plexands and antiplexes, which method'is flexible, capable of relatively sharp separation, `and. not highly demanding of attention and of utilities such as heat, refrigeration, pumping power and the like.

Other objects and advantages of the invention Will be apparent from the following description.

f 'f tures containing compounds characterizedv by a' VI. INVENTION IN DETAIL` As indicated above, it has been found that the:

foregoing objects are achieved by plexation with urea or thiourea of a plexand or plexands, the ureaor thiourea usedbeing acetic acid medium.

carried in an aqueous (l) Plectands and mztuies suitable for plantation The hydrocarbonI mixtures and oxygen-containing parain mixtures mentioned in the discussion of the prior art, above, are contemplated herein. So also are the compounds, plexands,

shown therein to havey the capacityto form plexads. This is subject to the condition that the compounds presentl in such mixtures are substantially inert, chemically, to the aqueous organic acid solutions, and particularly acetic acid solutions. V,For example, when urea is used vas a plexor, the mixture used may be: isomeric cresols (Kremanm Schotte .and Priewe); .oestradiols (Priewe); lutidine-picolines (Riethof); hydrocarbons containing straight vchain hydrocarbons of at least-six carbon atoms per molecule, and oxygen-containing mixtures containing straight chain acids, alcohols, aldehydes,.esters and/or ketonesV having atleast six carbon atoms per molecule (Bengen). It will be apparent from the denitions recited above, .that the plexands of these mixtures are the compounds forming plexads with urea, and that the antiplexes are 'the compounds which do not form urea plexads hydrocarbon mixtures containing n-parainsand n-olens, are prepared` bysynthesis withr vcarbon monoxide and hydrocarbons, i.e., typical Fischer- Tropsch products yprepared using cobalt and iron catalysts; cracked mixtures prepared by the vaporA phase cracking of stocks rich in n-parafins, such Y as.bythe cracking of parainic gas oils, footspil,

Vcrude waxes, etc.; mixtures containing straight, chain oxygenated compounds, such `as acids, alcohols, .aldehydes and esters, A. and ,containing currently herewith. Typical of the mixtures de-"f scribed in the latter application are mixtures con:

taining a straight-chain halide having the halogen atom attached to a terminal carbon and hav-` I ing at least about rive carbons in the chain. `Mix nitrogen-containingr substituent, are also advantageously plexated with the present process-subflject tothe proviso that the nitrogen-containing compounds present therein are insufficiently basic in character to react as a base with acetic acid;

such mixtures 'include' amides,` nitriles, nitroparaflins, etc. and are described in applicationv Serial No. 115,515, led concurrently herewith.`V

Sulfur-containing compounds present in various mixtures arealso plexated efliciently herein;

those are shown in application Serial No. 115,516, filed concurrently herewith, now abandoned. l

Compoundscontaining cyclic substituents, pre-' sent in various mixtures, are also efficiently plexated with urea in the present process,-being shown in application Serial No.,116,593,` filedy concurrently herewith. Plexation with urea off variousterminally substituted compounds frommI mixtures containing the same and non-terminally substituted compounds, described in rapplication e' Serial No.`115,517, led concurrently herewithfis Valso aided materially by the present process. =1

Urea plexation of a non-terminally monosubstituted compound from mixtures-'containing the same and a non-terminally poly-substituted compound, described in` application Serial 'No. 115,513, led concurrently herewith, isV alsoiinproved substantially by the present process'. Similarly, Amore' eiective resolution with urea of mixtures containing pararnic compounds of different degrees of unsaturation is realized herein; these mixtures are described in detailin applications Serial Nos. 115,514 and 115,518, iiled concurrently herewith.

With regard to thiourea plexation, the mixtures `shown in applications Serial Nos. 115,512 and 115,730, filed September 13 and 14, 1949, respectively are suitable in the present process. In Aapplication Serial No. 115,512, highly branched vparailins and/or highly branched olens are separated from straight chain orless highly branched compounds. In application Serial No. 115,730, certain cycloparaiiins and/or 'cyclo-olens are separated from mixtures hydrocarbons.

(Z) Pleor The plexors used herein include urea and thiourea and, as indicated above, these plexorsare used in organic acids, particularly 'in aqueous acetic acids, of certain concentrations. These branched compounds, .such as those obtained by synthesis from hydrogen and carbon monoxide over an iron catalyst or by oxidation of high molecular weight hydrocarbons; mixtures consisting essentially of n-parains and n-olei-lns, for the n-paramns form stronger plexads than the n-olens; mixtures consisting essentially of n-olens with the double bondin vvarious positions, for the olefins having the doublebond Other mixtures which may be moreerfectively` plexated with. urea by the A,present process `are those` containing hydrocarbon derivative s andv solutions should range from partially saturated.,- to supersaturated at` the temperature at .which they are contacted with a plexandor with a mixture containing oneor more plexands and antiplexes. In many cases, it will be found Iconvenient to suspend a further supply of urea or thiourea crystals in ther solution, handling it as a slurry. .A f

Acid solutions contemplatedl herein are substantially inert to thehydrocarbons and/or. hy-l i drocarbonk derivatives under treatment, and to urea or thiourea. They areheatstable, except to form salts with urea and thiourea, which salts are still reactive in plexation, both alone and in contact with the hydrocarbons,and hydrocar-f4 bon derivatives, at temperatures at which the 1 desired plexad is not heat stable.

of the same and other The acidV solutions; can.l be' usedr al'cmef orV with.`

another: solvent', providedA the, latten is notl so:- basicg-.as-to'form saltsrwithfthevacidi Itis often advantageousn to utilize;- (particularly` when the plexad isz separated by gravity) a multi-com'.-

ponent solvent.system;.with the acid solutions) in:

combination' with': alcohols, glycolsgethers; acids, amides, nitriles, etc'. Typical oft such solvents are: ,r methanol, ethanol, propanol, ,ethylene glycol. butylene glycols, ethylene glycol dimethyl' ether, form-amide,- orrnic acid; acetonitrilaxetc: SuchA multi-componentisolvents.- partially saturated to supersaturated',withturean or thiourea', lendgthemf selves readily to a continuous process forrseparation' byL plexation.

It is'also-contemplatedh hereinV to include a small quantity oa suracefactive agent in. theV ureaor thiourea solution, in^` the manner. deY

scribedin copending. applicationxSerial No. 115;- 437; filed concurrently herewith.

Another modification contemplated herein: is` theaprocedure described in1 copendingapplication Serial No. 137,739,I filedf Januaryv 10, 1950, involvingcontact of` hydrocarbons andforhydro'- carbon derivatives with a; plexor impregnated upon. a porous support:v Inv this` modication, thef solvents` used withn the hydrocarbonV andyor hydrocarbon derivatives will beV acid solutions such as?. described herein.

Anunderstanding of a preferred embodiment ofi'tl'iisv invention may befacilitated by reference tothe accompanying illustrative drawing, Figure 1,. which: isA a1 schematic. flow-diagram 01* one specic arrangementif or `practicingv the invention. Y

InA Figure 1, av mixture of hydrocarbons suchY Si, sults of these examplesare set-fortuin the table.

from; settler: I'Iz through".

III can be recycled'. throughilinei. I.;

From separator; Il,k aqueous urea is takenl through line I5to. a-.tower Vor still I6 wherein urea is concentrated. Water is removed through line I1, andV al concentrated aqueous urea is removed through line I8, andV is taken tliroughcooler I9 to line I or'reuse;

2,3-Dimethyl octane, together settler. 20, and aqueous acetic.. acid is removedthrough line ZI to tank i4. Recovered aqueous acetic acid can be recycled as indicated above. 2,3-Dimethyl octane is removed through line 22.-

As shown above, a urea-n-decane'plexad can" be decomposed or resolved to urea andn-decane,

under'the influenceofwater and heat. Plexads; l

v1. ILLUSTRATIVE EXAMPLES:

Several illustrative examples are provided' byn the following. Ten parts, by volume, of concentrat'ed urea solution and; two'parts; byfvolume, of a n-paraidn were stirred vigorously at 25 C.` in a reaction vessel. Theextentotreactionwas indicated by thetemperature rise and` the reaction `speed was indicated by the; time requiredl for such temperature increase; Re"- asn-decaneand'2,3dimethyl octanev and aureaaqueous acetic acid solution, is introduced through line I to plexation tank 2. The mixture1in tank.2 is agitated for a suitable period of time, generally from several Ininutes'to.A about three hours, at a suitable temperature, for example 25 C., in order to realize a satisfactory degree of plexation. It will be understood that plexation tank 2 is equippedwith a suitable stirrer or agitator (not shown). The resultinglmixture is taken fromtank 2 through line 3, to separator 4.y The separator, 4, can be a centrifuge, lter; settler equipped with a suitable screw conveyor, etc. as will be understood by those skilled in the art.

Antiplex, 2,3dimethyl octane), together with some aqueous acetic acid, is withdrawn from separator 4 through line 5; and urea-n-decane plexad, together with some aqueous acetic acid, is withdrawn through line I5.V The urea-n-decane plexad in line 6 is contacted with hot water (at about'70" C.) which is added through line l, and is passed through heat exchanger tto separator 9. The heat exchanger 8 is maintained at aboutV '70r C., such that the urea-n-decane plexad is decomposed or resolved. n-Decane is removedv from separator Sithrough line I0 and is introduced into settler II. n-Decane is removed' It is tobe noted that thev foregoing results'were obtained by using an operating'temperature of'l about'25" C. It is to be understood, however, that plexation can be effected at higher-or'lower temperatures. For example, at-temperaturesofabout 40 C. anhydrous acetic acid can be used;

At temperatures of the order of 40 C., aceticacidY solutions range from about 20 Weight per cent'to anhydrous or glacial acetic aci-d. Correspondingly, at lower temperatures, as at about 10f'C.,

the" range of concentrationY isV advantageously from about 20 weight per cent to about-70 weight v per cent.

I claim:

1. In* theseparation of al compound (I) having the capacity to formA aA crystalline complex with ay complexeforming agent selected fromthe group consisting of urea and.thiourea, from a f medium determined by those Acontainin'gffro'm about 20' per' cent byV Weight: of acetic' acid ftolinee I 2; Aqueoussaceti. acidV removed' throughtlinei.- I0; to settlerf II; Withf: the` nr-decane is. takenA to l tank; I4: through.. line; i I 3. Recovered laqueous YaceticiacidLstored initank with some= aqueous acetic acid in line 5, is'intro'duced `into about 70 per cent by weight when said contact is affected at about C., to about 88 per cent by weight when said contact is aiected at about 25 C., and to 100 per cent by weight when said contact is aiected at about 40 C.

2. In the separation of a compound (I) having the capacity to form a crystalline complex with a complex-forming agent selected from the group consisting of urea and thiourea, from a mixture containing said compound (I) and a compound (II) incapable of forming a crystalline complex with the same said agent, whereby said compound (I) preferentially forms a complex with said agent, and wherein said complex and compound (II) are separated, the improvement which comprises: so contacting said mixture and said agent in an aqueous acetic acid medium containing about 50 per cent by weight of acetic acid.

3. In the separation of a compound (I) having the capacity to form a crystalline complex with urea, from a mixture containing said compound (I) and a compound (II) incapable of forming a crystalline complex with urea, whereby said compound (I) preferentially forms a complex with urea, and wherein said complex and compound (II) are separated, the improvement which comprises: so contacting said mix-` ture and urea in an aqueous acetic acid mediumY containing from about 20 to 88 per cent by weight of acetic acid.

4. In the separation of a compound (I) having the capacity to form a crystalline complex with thiourea, from a mixture containing said compound (I) and a compound (II) incapable of forming a crystalline complex with thiourea, whereby said compound (I) preferentially forms a complex with thiourea, and wherein said comagent, whereby said hydrocarbon (I) preferen-A tially forms a complex with said agent, and

wherein said complex and hydrocarbon (H) are separated, the improvement which comprises: so contacting said mixture and said agent in solution in an aqueous acetic acid medium containing from about 20 to about 88 per cent by Weight of acetic acid.

6. The method of forming a crystalline complex of a compound (I) having the capacity to 10 form a crystalline complex with a complex-forming agent selected from the group consisting of urea and thiourea, which comprises: contacting said compound (I) with said agent in an aqueous acetic acid medium determined by those containing from about 20 per cent by weight of acetic acid to about 70 per cent by weight when said contact is affected at about 10 C., to about 88 per cent by weight when said contact is aiected at about 25 C'., and to 100 per cent by weight when said contact is affected at about 40 C.

7. The method of forming a crystalline complex of a compound (I) having the capacity to form a crystalline complex with urea, which comprises: contacting said compound (I) with urea in an aqueous acetic acid medium containing from about 20 to 88 per cent by weight of acetic acid.

8. The method of forming a crystalline complex of a compound (I) having the capacity to form a crystalline complex with thiourea, which comprises: contacting .said compound (I) with thiourea in an aqueous acetic acid medium containing fromabout 20 to 88 per cent by weight of acetic acid.

9. 'Ihe method of forming a crystalline complex of a compound (I) having the capacity to form a crystalline complex with a complex-forming agent selected from `the group consisting of urea and thiourea, which comprises: contacting f said compound (I) with said agent in an aqueous organic acid medium having a hydrogen ion concentration from about 10-3 to about 10-1.

10. In the separation of a compound (I) having thecapacity to form a crystalline complex with a complex-forming agent selected from the -groupconsisting of urea and thiourea, from a mixture containing said compound (I) and a compound (II) incapable of forming a crystalline complex with the same said agent, whereby said compound (I) preferentially forms a complex with said agent, and wherein said complex and compound (II) are separated, the improve- References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 2,520,716 Fetterly Aug. 29, 1950 2,578,054 Fetterly Dec. 11, 1951 OTHER REFERENCES Bengen,` German Patent application O. Z. 12,438, March 18, 1940, U. S. publication date May 22, 19416; Urea Complex Digest, 

1. IN THE SEPARATION OF A COMPOUND (I) HAVING THE CAPACITY TO FORM A CRYSTALLINE COMPLEX WITH A COMPLEX-FORMING AGENT SELECTED FROM THE GROUP CONSISTING OF UREA AND THIOUREA, FROM A MIXTURE CONTAINING SAID COMPOUND (I) AND A COMPOUND (II) INCAPABLE OF FORMING A CRYSTALLINE COMPLEX WITH THE SAME SAID AGENT, WHEREBY SAID COMPOUND (I) PREFERENTIALLY FORMS A COMPLEX WITH SAID AGENT, AND WHEREIN SAID COMPLEX AND COMPOUND (II) ARE SEPARATED, THE IMPROVEMENT WHICH COMPRISES: SO CONTACTING SAID MIXTURE AND SAID AGENT IN AN AQUEOUS ACETIC ACID MEDIUM DETERMINED BY THOSE CONTAINING FROM ABOUT 20 PER CENT BY WEIGHT OF ACETIC ACID TO ABOUT 70 PER CENT BY WEIGHT WHEN SAID CONTACT IS AFFECTED AT ABOUT 10* C., TO ABOUT 88 PER CENT BY WEIGHT WHEN SAID CONTACT IS AFFECTED AT ABOUT 25* C., AND TO 100 PER CENT BY WEIGHT WHEN SAID CONTACT IS AFFECTED AT ABOUT 40* C. 